The proposed research is a long-term project to purify and characterize the transformation-specific feline oncornavirus membrane antigen (FOCMA) which is on the surface of feline leukemia virus (FeLV) and feline sarcoma virus (FeSV) transformed cells and is involved in tumor immunity; and to study expression of genes for FOCMA through analysis of virion and intracellular virus-specific mRNA species and their in vivo and cell-free translation. Protein purification and characterization will focus on physical, chemical, and immunologic properties of FOCMA using standard methods of protein chemistry and immunology to provide antisera, purified FOCMA and information needed for subsequent work on intracellular antigen synthesis, processing, and assembly, as well as on cell-free synthesis of FOCMA. The same materials will be used to develop faster and more sensitive assays for FOCMA and its antibody and to assess directly the role of the purified antigen and its monospecific antibody in immune protection and immune therapy against tumors. Virus-specific RNAs in FOCMA positive nonlymphoid cells productively and nonproductively transformed by FeLV will be analyzed by analytical cDNA probes to determine their amounts, number, size, and location in the cell. Using a preparative mercurated cDNA probe in conjunction with SH-agarose, intracellular virus-specific RNA will be purified free of cell RNA in quantity and quality sufficient for chemical analysis and for cell-free translation to determine its role as mRNA for FOCMA. Translation of intact and fragmented FeLV and FeSV virion RNA and various size intracellular viral mRNAs in mRNA dependent systems will be done to determine the coding potential of the entire genome and the translation products of each purified viral mRNA, with emphasis on determining the nature of the RNA coding for FOCMA and/or transforming gene-specific polypeptides.